全文获取类型
收费全文 | 1211篇 |
免费 | 90篇 |
专业分类
电工技术 | 3篇 |
综合类 | 3篇 |
化学工业 | 408篇 |
金属工艺 | 15篇 |
机械仪表 | 22篇 |
建筑科学 | 74篇 |
能源动力 | 30篇 |
轻工业 | 340篇 |
水利工程 | 24篇 |
石油天然气 | 10篇 |
无线电 | 30篇 |
一般工业技术 | 152篇 |
冶金工业 | 86篇 |
原子能技术 | 2篇 |
自动化技术 | 102篇 |
出版年
2024年 | 2篇 |
2023年 | 14篇 |
2022年 | 54篇 |
2021年 | 76篇 |
2020年 | 38篇 |
2019年 | 44篇 |
2018年 | 51篇 |
2017年 | 52篇 |
2016年 | 54篇 |
2015年 | 51篇 |
2014年 | 45篇 |
2013年 | 87篇 |
2012年 | 78篇 |
2011年 | 97篇 |
2010年 | 81篇 |
2009年 | 69篇 |
2008年 | 46篇 |
2007年 | 56篇 |
2006年 | 48篇 |
2005年 | 30篇 |
2004年 | 29篇 |
2003年 | 27篇 |
2002年 | 26篇 |
2001年 | 12篇 |
2000年 | 8篇 |
1999年 | 11篇 |
1998年 | 10篇 |
1997年 | 13篇 |
1996年 | 10篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 5篇 |
1992年 | 5篇 |
1989年 | 3篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1983年 | 7篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1980年 | 3篇 |
1979年 | 6篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 4篇 |
1961年 | 5篇 |
1960年 | 2篇 |
1959年 | 1篇 |
排序方式: 共有1301条查询结果,搜索用时 15 毫秒
991.
Many companies move from open-plan offices (OPO) to activity-based workplaces (ABWs). However, few studies examine the benefits and drawbacks following such a change. The aim of this study was to explore how physical conditions, office use, communication, privacy, territoriality, satisfaction and perceived performance change following a company’s relocation from an OPO to an ABW. A mixed methods approach included pre- and post-relocation questionnaires and post-relocation focus groups, individual interviews and observations. The questionnaires enabled comparisons over time (n = 34) and broader analyses based on retrospective ratings of perceived change (n = 66). Results showed that satisfaction with auditory privacy, background noise, air quality, outdoor view and aesthetics increased significantly after relocation. Negative outcomes, such as lack of communication within teams, were perceived as being due to the high people-to-workstation ratio and lack of rules. Overall satisfaction with the physical work environment increased in the ABW compared to the OPO. Perceived performance did not change significantly.
Practitioner Summary: Activity-based workplaces (ABWs) are commonly implemented although their effects on performance and well-being are unclear. This case study gives advice to stakeholders involved in office planning. Despite shortcomings with the people-to-workstation ratio and rules, employees showed improved satisfaction with auditory privacy and aesthetics in the ABW compared with the previous open-plan office. 相似文献
992.
Armejach Adrià Caminal Helena Cebrian Juan M. Langarita Rubén González-Alberquilla Rekai Adeniyi-Jones Chris Valero Mateo Casas Marc Moretó Miquel 《The Journal of supercomputing》2020,76(3):2039-2062
The Journal of Supercomputing - Data-level parallelism is frequently ignored or underutilized. Achieved through vector/SIMD capabilities, it can provide substantial performance improvements on top... 相似文献
993.
A new stochastic volatility model, called A-LMSV, is proposed to cope simultaneously with leverage effect and long-memory in volatility. Its statistical properties are derived and compared with the properties of the FIEGARCH model. It is shown that the dependence of the autocorrelations of squares on the parameters measuring the asymmetry and the persistence is different in both models. The kurtosis and autocorrelations of squares do not depend on the asymmetry in the A-LMSV model while they increase with the asymmetry in the FIEGARCH model. Furthermore, the autocorrelations of squares increase with the persistence in the A-LMSV model and decrease in the FIEGARCH model. On the other hand, if the correlation between returns and future volatilities is negative, the autocorrelations of absolute returns increase with the magnitude of the asymmetry in the FIEGARCH model while they decrease in the A-LMSV model. Finally, the cross-correlations between squares and original observations are, in general, larger in absolute value in the FIEGARCH model than in the A-LMSV model. The results are illustrated by fitting both models to represent the dynamic evolution of volatilities of daily returns of the S&P500 and DAX indexes. 相似文献
994.
Mohsen Besharat Reza Tarinejad Mohammad Taghi Aalami Helena M. Ramos 《Water Resources Management》2016,30(8):2687-2702
Air chambers show good ability in controlling the pressure surge from a water hammer (WH) phenomenon. To simulate an air chamber and study the behavior of air inside it, a compressed air vessel (CAV) is considered in a pressurized system. The current work consists of experimental tests and one-dimensional (1D) and two-dimensional (2D) computational fluid dynamics (CFD) simulations for an air pocket within a CAV in the case of rapid pressurization and the occurrence of WH in a pressurized system. The pressure variations create vorticity and turbulence with oscillating behaviors, but the available 1D models are unable to simulate those phenomena adequately. Therefore, by using the measured data, proper CFD analysis is conducted considering the effect of the wall, y + , mesh size, turbulence, and the wall treatment method to better understand the behavior of the system. Results of the CFD simulation show that realizable k-ε turbulence model, when coupled with the enhanced wall treatment (EWT) method, works adequately for modeling the pressure oscillation. The volume of fluid (VOF) model and the piecewise linear interface calculation (PLIC) method have presented good ability in the prediction of the air-water interface. 相似文献
995.
Helena Pongrac 《Multimedia Systems》2008,13(4):297-307
High-frequency vibrations are an essential part of numerous manipulation tasks. A promising research area, in particular,
are telemanipulation tasks where vibrations occurring in the remote environment are fed back through tactile displays. Three
experiments concerning the perception of vibrations were conducted. The first experiment aims at determining whether vibrations
are coded primarily by frequency, amplitude, or acceleration by human participants. Results show that primarily frequency
and amplitude, but not acceleration of the vibrations were perceived. In the second experiment, participants’ just noticeable
difference (JND) for frequency under different conditions was examined. The resulting JND of 18% for frequencies showed dependence
neither on the amplitude or acceleration, which were independently held constant, nor on the reference frequencies. Therefore,
it is not necessary to adjust the subjective intensity for vibrations for each human operator when designing and using tactile
displays. In the third experiment, the stimuli and the procedure of the second experiment were replicated using different
configurations and a mere force-output device. The resulting JNDs were 21% for vibrations of 100 Hz, and 17% for vibrations
of 150 Hz and above. Furthermore, there was no visual dominance over the haptic modality regarding the JND for frequencies. 相似文献
996.
The influence of oxidation on complex paramagnetic centres system of demineralized coal and coal free of pyrite was compared. Polish orthocoking coal with a carbon content of 87.8 wt% was studied. This coal was oxidized with nitric acid (HNO3), peroxyacetic acid (PAA) and in O2/Na2CO3 system. Multi-component structure of X-band EPR spectra of the coal samples was numerically analysed. The lineshape and the parameters of the component lines: linewidths and g-factors, were determined. Concentrations of paramagnetic centres were measured. The three groups of paramagnetic centres belonging to different molecular units were found in the studied samples. They were responsible for broad Gauss (ΔBpp: 0.49-0.84 mT), broad Lorentz 1 (ΔBpp: 0.18-0.35 mT), and narrow Lorentz 3 (ΔBpp: 0.04-0.08 mT) EPR lines. Properties of paramagnetic centres of the simple molecular units with broad Gauss and Lorentz 1 lines were changed during demineralization of coal and after pyrite removing from coal. g-Values of Gauss and Lorentz 1 lines increased, Lorentz 1 lines were broadened and concentrations of paramagnetic centres with Lorentz 1 lines increased. Oxidation of both demineralized coal and coal free of pyrite with nitric acid led to the highest decrease of the concentration of paramagnetic centres with Gauss lines, narrowing of these lines and increase of g-factor. The higher effects of oxidation on paramagnetic centres responsible for broad lines were observed for coal free of pyrite. Paramagnetic centres with narrow Lorentz 3 lines belonging to multi-ring aromatic units in demineralized coal and coal free of pyrite were not susceptible for oxidation. 相似文献
997.
Internet use and non-use: views of older users 总被引:1,自引:0,他引:1
This paper reports the results of two connected surveys of computer and Internet use among the older population in the UK.
One hundred and twenty questionnaires and interviews were completed with participants aged over 55 in Derbyshire and 353 questionnaires
and interviews with over 50s in Scotland. Rates of use, computer and Internet activities, and reasons for use and non-use
were investigated. These were backed up by four semi-structured interviews with IT trainers, describing experiences and issues
of training this age group. The results indicate a “grey” digital divide, with many older people missing out on the benefits
that computers and the Internet can provide. They also indicate some of the reasons why older people do not use computers
and the Internet more. These suggest some practical ways forward, highlighting the importance of changing older people’s misconceptions
about computers, better informing them about what they are, what they can do and how they can be of real practical use.
相似文献
Joy Goodman (Corresponding author)Email: |
998.
I Aksentijevich E Pras L Gruberg Y Shen K Holman S Helling L Prosen GR Sutherland RI Richards M Dean 《Canadian Metallurgical Quarterly》1993,53(3):644-651
Familial Mediterranean fever (FMF) is an autosomal recessive disease causing attacks of fever and serositis. The FMF gene (designated "MEF") is on 16p, with the gene order 16cen-D16S80-MEF-D16S94-D16S283-D16S291-++ +16pter. Here we report the association of FMF susceptibility with alleles as D16S94, D16S283, and D16S291 among 31 non-Ashkenazi Jewish families (14 Moroccan, 17 non-Moroccan). We observed highly significant associations at D16S283 and D16S291 among the Moroccan families. For the non-Moroccans, only the allelic association at D16S94 approached statistical significance. Haplotype analysis showed that 18/25 Moroccan FMF chromosomes, versus 0/21 noncarrier chromosomes, bore a specific haplotype for D16S94-D16S283-D16S291. Among non-Moroccans this haplotype was present in 6/26 FMF chromosomes versus 1/28 controls. Both groups of families are largely descended from Jews who fled the Spanish Inquisition. The strong haplotype association seen among the Moroccans is most likely a founder effect, given the recent origin and genetic isolation of the Moroccan Jewish community. The lower haplotype frequency among non-Moroccan carriers may reflect differences both in history and in population genetics. 相似文献
999.
Co‐administration of Antimicrobial Peptides Enhances Toll‐like Receptor 4 Antagonist Activity of a Synthetic Glycolipid 下载免费PDF全文
Dr. Fabio A. Facchini Dr. Helena Coelho Stefania E. Sestito Dr. Sandra Delgado Alberto Minotti Prof. David Andreu Prof. Jesús Jiménez‐Barbero Prof. Francesco Peri 《ChemMedChem》2018,13(3):280-287
This study examines the effect of co‐administration of antimicrobial peptides and the synthetic glycolipid FP7, which is active in inhibiting inflammatory cytokine production caused by TLR4 activation and signaling. The co‐administration of two lipopolysaccharide (LPS)‐neutralizing peptides (a cecropin A–melittin hybrid peptide and a human cathelicidin) enhances by an order of magnitude the potency of FP7 in blocking the TLR4 signal. Interestingly, this is not an additional effect of LPS neutralization by peptides, because it also occurs if cells are stimulated by the plant lectin phytohemagglutinin, a non‐LPS TLR4 agonist. Our data suggest a dual mechanism of action for the peptides, not exclusively based on LPS binding and neutralization, but also on a direct effect on the LPS‐binding proteins of the TLR4 receptor complex. NMR experiments in solution show that peptide addition changes the aggregation state of FP7, promoting the formation of larger micelles. These results suggest a relationship between the aggregation state of lipid A‐like ligands and the type and intensity of the TLR4 response. 相似文献
1000.
Antonio Anax Falcão de Oliveira Tiago Franco de Oliveira Michelle Francini Dias Marisa Helena Gennari Medeiros Paolo Di Mascio Mariana Veras Miriam Lemos Tania Marcourakis Paulo Hilário Nascimento Saldiva Ana Paula Melo Loureiro 《Particle and fibre toxicology》2018,15(1):40